The present invention relates both to a method for obtaining a sleeve for mounting flexographic printing plates, and to the sleeve itself.
Italian patent 1,293,502 describes a sleeve for mounting printing plates on flexographic printing machine cylinders. It refers to a sleeve formed from a transparent flexible polymer film or sheet substantially indeformable in its plane, such as polyester, and constituting the development of all or part of the cylinder on which the sleeve is applied by strips of adhesive tape. The patent describes the operability, use and advantages of this known sleeve.
The sleeve proposed in that patent is composed of a single material, i.e. a single layer, and presents a problem deriving from the thickness difference due to the application of the double-sided adhesive tape for fixing the sleeve to the printing cylinder. This problem is of considerable importance because it prejudices production of high quality printing work and also does not enable optimum printing of continuous work or total background work (where the edges of the photopolymer (plate) join together to obtain a continuous print over the entire cylinder surface).
Other currently available known solutions, mainly empirical, are hardly practical and are used for low profile or low quality work in that they present even more serious thickness difference problems and in particular do not enable efficient fixing to the cylinder, so totally prejudicing the entire print quality.
The main object of the present invention is to improve the known sleeve by proposing both a method for producing an improved sleeve and the improved sleeve itself, by which better fixing to the printing cylinder is achieved.
Another object of the present invention is to provide a sleeve, of which that surface to be fixed to the cylinder is substantially uniform, so eliminating any printing problem while at the same time improving the print quality.
A further important object of the present invention is to provide a sleeve for all types of printing work (whether of low or very high quality) applicable to all types of commercially available printing machines, whether of central impression, stack or in-line with extruder type, using either traditional iron cylinders or rubber sleeves.
These and further objects which will be apparent from the ensuing detailed description are attained by the invention on the basis of the technical teachings expressed by the accompanying claims.